beta-Endorphin secretion of arginine vasopressin in vivo

The effect of beta-endorphin upon plasma arg8-vasopressin release was studied in vivo in rabbits and in vitro in rat neural lobes. Following intravenous administration of 200 mug/kg synthetic beta-endorphin plasma AVP rose significantly by five minutes after injection and remained elevated for twenty-five minutes compared to controls. In contrast beta-endorphin had no significant effect on AVP release from isolated rat neural lobes in vitro. beta-Endorphin stimulates AVP secretion in vivo, but this is not due to a direct action upon the neural lobe.